The full efficiency and overall operational capability of many low pressure, short pulse laser systems is not realized due to the fact that a significant fraction of the excitation produced in the gas is not transferred to the lasing gas component. In some laser systems, such as the 14 micron and 16 micron CO.sub.2 laser systems described in U.S. Pat. No. 4,168,474, issued Sept. 18, 1979 and pending application Ser. No. 863,193, filed Dec. 22, 1977, both assigned to the assignee of the present inventions and incorporated herein by reference, the excitation of the lasing atomic or molecular species is produced at least in part by energy transfer from a second excited atomic or molecular species. The second species is referred to as a transfer gas and can be excited by a number of methods such as electric discharge, electron beam, optical pumping, and so forth. These excitation processes may also tend to excite the lasing gas medium directly. In CO.sub.2 laser systems, as referred to above, the energy transfer process is frequently used to excite the CO.sub.2 molecules. Nitrogen is typically used as the transfer gas in these laser systems.
In order to achieve a higher efficiency from these laser systems it is necessary to transfer a larger fraction of the energy from the transfer gas to the lasing gas. This is particularly true for lasers operating in a short pulse output mode. In conventional CO.sub.2 lasers operating at high pressures, i.e. greater than 300 Torr, it is possible to achieve efficient energy transfer during a relatively short, i.e., 1-3 .mu.sec., laser output pulse because the energy transfer process is fast compared to the laser output pulse length. In other laser systems, such as a 16 micron CO.sub.2 bending mode laser described in the above-referenced U.S. Patent and pending application, that operate at pressures less than 300 Torr and relatively short laser extraction output pulses, i.e., less than 1-3 .mu.sec., the energy transfer process is slow compared to the laser output pulse length and a significant fraction of the excitation energy stored in the transfer gas is never used. There is described below with reference to the accompanying drawings a technique for overcoming this shortcoming in realizing improved efficiency in low pressure and short pulse output mode operation laser systems.